Giant balloon measures cosmic rays

Emma Woollacott, 22nd May 2009

Kiruna, Sweden - A 400-foot balloon is now flying at the edge of space to collect data on cosmic rays - the most super-charged particles in the universe.

University of Delaware researchers launched the balloon, which is 396 feet tall and 459 feet in diameter when fully inflated, last week from Sweden's Esrange Space Center in the Arctic Circle. It is flying at a speed of more than 40 knots at an altitude of nearly 27 miles. Its payload of cosmic ray detectors, housed in a pressurized shell, will be cut free in northwestern Canada and float back down to Earth on a parachute.

Cosmic rays are extraterrestrial high-energy electrons, protons, and heavier nuclei. About a thousand strike every square meter of Earth's atmosphere each second.

“The bulk of cosmic rays are likely produced by strong shock waves from supernova explosions within our galaxy,” said John Clem, research associate professor of physics and astronomy at the University of Delaware's Bartol Research Institute. “It is well documented that these high-energy particles can threaten the health of astronauts in space and expose airline workers to radiation."

With support from NASA, the team is launching two helium-filled high-altitude balloons - one to carry the Low Energy Electrons (LEE) instrument payload, which is now afloat, and one to carry the Anti-Electron Sub-Orbital Payload (AESOP), which will be launched tomorrow and travel to the upper limits of the atmosphere.

AESOP can detect electrons with energies up to about 10 gigaelectron volts, according to Clem, and uses a system of different radiation detectors and a magnetic spectrometer to identify the particle's electric charge, energy, and mass.

The data will be used to study solar modulation, the variation in cosmic ray intensity that is correlated with the 11-year cycle of solar activity. As solar activity rises, cosmic ray activity decreases. Currently, solar activity is low, and we are in a period of high cosmic ray intensity, Clem said.

“We're working to better understand how the sun's changing magnetic field affects cosmic ray propagation through the solar system,” Clem said.